Safety device for electrical circuits



(No Model.) 2 Sheets-Sheet 1.. W. J. HAMMER.

SAFETY DEVICE ECE ELECTRICAL CIRCUITS.

No. 397,715. Patented Feb. 12, 1889.

(No Model.)

` 2 Sheets-Sheet 2. W.*J. HAMMER.

S'AIE'IYY DEVICE FCR ELECTRICAL CIRCUITS.

No. 397,715. Patented I'eb.12, 1889.

UNITED STATES PATENT tlEEIcE.

lV I l. l. l A )l J'.

HAMMER, OE BOSTON, MASSACHUSETTS SAFETY DFE-.WCE i-R LECTRiCAl. ClRCUiTS.

SPECFICATION' for .13 part of Letters Patent No. 397,715, dated 'February 12, 1889.

Application filed November 19, 1886. Serial No. 219,368. (No model.)

tribution, and my invention consists, mainly,

in the use, with a conductor of a circuit, of two or more safety-catches, usuallyT of different sizes, and a suitable switching device whereby any one of said safety-catches may be interpolated in the circuit of such conductor, whereby when the safety-catch in circuit is destroyed, in consequence of a cross or of too heavy a load on the circuit, another and preferably one of greater conducting capacity may be switched in to takeits place.

In the Edison system of electrical distribution, as is now well known, circuits called feeding-circuits extend from the source of supply to which they are all connected to a system of connected positive and negative main or lighting conductors. Each of these feeding-circuits has heretofore been provided with a safety-catch. if the load lupon any feeder becomes too great for its conducting l a circuit of any electric lighting or other eleccapacity,its safety-catch is fused, and all the current passes over the remaining feeders; l but this may have the effect of overloading i one or more other feeders, whose safety-catches may be in turn destroyed, and so on until all the feeding-circuits are broken and the supply of current is entirely cut off. This once actually occurred in the Edison distributing system in New York city, when all the lamps feeder.

a heavier one maybe immediately switched into its place by thc attendant at the station,

so that the circuit is practically uninterrupted.

trieal system is required to convey at. different times current for a greater or less number of lamps or varying amounts of current. By my invention such a circuit Inay always be provided with a safety-catch of a size adapted to the load upon it..

My invention is illustrated in theaccompa-v nying drawings.

Figure l is a plan view of apparatus embodying said invention in which a pivoted switch is employed; Fig. 2, a central vertical section thereof; and Figs. and t are similar views of a form of the invention employing` a plug-switch.

Referring first to Figs. lV and 2, .i is a suitable insulating-base, on which the parts of the apparatus are mounted, and which adapted to be secured by means of screws or otherwise upon a wall or in other convenient situation. Attached to said base near one end is an arcshaped metal plate, from which, beyond the end of the base, extends a metal sleeve, o, adapted to receive an electrical conductor which is held therein by set-screws b.

C, t", and C? are metal contact-plates sccured tothe base A, and preferably of the double form shown, so that the metal switcharm D enters between the two parts of a plate, so as to make good contact therewith, the upper tongues, c, of the plates being split to make a spring-pressure upon the switch-arm. Such switch-arm has anv insulating-handle, E, for moving it, and is pivoted, as shown, the pivot d passing through a plate, c, Vfrom which extends a sleeve, o', provided with set-screws b b for receiving the circuit-wire. The arm may be provided with a flat spring. c', to assist its contact. The contact-plates L". C. and

, C'2 are connected with the plate ll, respectively, in the district were extinguished in consequence of the original overloading of a single by fusible safety-catch strips E. F', and El, which strips are removably held upon the Iplates by thumb-nuts f f. These safety- )ly invention is designed mainly to overcome this dillicnlty, since by its use as soon as any safety-catch is destroyed another and l My invention is, however, as stated, adapted i for use in other situations-for instance, where Catches are preferablyof different sizes, so that they are adapted to convey, without fusing, different amounts of current, the amounts oi' current being marked upon them in the drawings to illustrate this. As shown, the circuit will be through the middle strip, l1" g but if this strip should be destroyed. or if the circuit should be required to convey a greater IOO or less amount of current, the switch-arm is shifted to one side or the other, so as to throw in another strip of the desired size.

In the form shown in Figs. 3 and i the base Alias upon it a plate, (l, connected by the safety-catches'F, lf", and lf2 with plates 7i 71, h2, any one of which is adapted to be joined by the insertion of a suitable plug, ll, with the plate l. The plate G- has extendin from it the sleeve u, and the plate l the sleeve u, whereby the condncting-wircs are connected to the device. ,2y shiftingl ihe plug the different safety-catches are conected in series in the same way as by the movement of the pivoted switch-arm in the first-described form. The plug` is preferably provided with a short screw-thread, 1', and the shoulders k on the plates between which it is inserted have similar screwthreads, whereby when the plug is inserted it maybe given a slight turn, so that it will be held securely in position and cannot be accidentally dislodged or loosened by the jarring` of the switch. This form of conneeting jplug` is evidently adapted for use in other situations in electrical apparatus.

Vhat I claim isl. The combination, with a broken eonl ductor of an electrical circuit, of two or more l fusible safety-catches, all connected in parallel circuit with .one terminal of said conductor, and a switching' device for connecting' the other end of any one of said safety-catches with the other terminal of said conductor, substantially asset forth.

The combination, with a broken conductor of an electrical circuit, of two or more fusible safety-catches, all connected in parallel circuit with one terminal of said conduetor, and a pivoted switch-arm connected with the other terminal and adapted to be brought into connection with any one of said safetv-catches, substantially as set forth.

3. The combination of -the insulating-base, a circuit-terminal at one end thereof, two or more separate contact-plates on the base, fusible safety-catches j oining said contactplates with said terminal, another terminal at the other end ot' the base, and a switehingdevice for connecting' said last-named terminal, substantially as set forth.

i. The combination, with the conductor ol' an electrical circuit, of two or more fusible safety-catches of different comlnctingx capacities, and a switching' device lor interpolating` any one of them in the circuit of said conductor, substantially as set forth.

This specification signed and witnessed this lTth day of ovcniber, 1886.

WM. J'. llltlMER. ll'itnesses:

WM. F. SoNN, W. C. Law'roN. 

